observable/src/com/android/tools/idea/observable/core/ObservableOptional.java

/*
 * Copyright (C) 2017 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.android.tools.idea.observable.core;

import com.android.tools.idea.observable.ObservableValue;
import org.jetbrains.annotations.NotNull;
import org.jetbrains.annotations.Nullable;

import java.util.Optional;

/**
 * Read-only handle to an {@link OptionalProperty}.
 * <p/>
 * Designed with an interface that emulates Guava's {@link Optional}.
 */
public interface ObservableOptional<T> extends ObservableValue<Optional<T>> {

  @NotNull
  T getValue();

  @NotNull
  T getValueOr(@NotNull T defaultValue);

  @Nullable
  T getValueOrNull();

  @NotNull
  ObservableBool isPresent();
}